It is projected that 44% of persons who turned age 65 in 2000 will enter a nursing home (NH) before death;23% will spend >1 year there;and the number of individuals admitted to a NH will double by 2020. NH residency is an important risk factor for venous thromboembolism (VTE) and death following VTE, and NH residency independently accounts for 13% of all VTE cases in the population. Much of the information on VTE incidence, risk factors, and consequences has come from the unique medical records-linkage system of the Rochester Epidemiology Project (REP). As the NH population increases, the incidence of VTE is expected to rise;likewise, prevention of VTE and its consequences within the NH population could substantially reduce the burden of VTE within the population generally. However, information needed to inform predictions of resource use and decisions regarding appropriate resource allocation is lacking. There are very few estimates of VTE incidence rates among NH residents, and no estimates of the relative hazard of death associated with VTE in the NH setting (Aim1). The incidence among high risk patients can be markedly reduced with prophylactic anticoagulation. However, absent better methods of targeting prophylaxis, the vast majority of persons with a clinical risk factor for VTE are needlessly exposed to potentially serious, even fatal, complication from anticoagulation. The overall benefit-to-cost ratio of prophylaxis of NH residents may be less than that for the population generally. In order to focus prevention strategies in the NH setting, there is a need to identify residents at greatest risk of VTE and those for whom prevention is likely to yield the greatest benefit (Aim2). An appreciation of the consequences of VTE and VTE prevention within the NH population also requires data on rates of VTE complications, treatment, associated side effects, and economic outcomes (Aims 3 &4). We propose to take advantage of a unique opportunity to combine information on NH person-years at risk and potentially important risk factors for VTE (e.g., disability and mobility limitations), as contained within NH administrative datasets, with the rich clinical detail afforded by REP resources. We will identify all Olmsted County residents admitted to local nursing homes 1988-2005, characterize them as to risk based on standardized measures obtained at periodic assessments throughout their stay, and calculate VTE incidence and survival rates. Data from both sources will allow us to address the question, "What is it about being in a NH that contributes to increased risk of VTE?";to describe patterns of VTE treatment, morbidity, and mortality for NH cases and compare these patterns with those obtained separately for community-dwelling cases, and to estimate the economic consequences of VTE. This proposal will provide previously unavailable estimates of the burden of VTE within the NH population. The information gained is essential for informing efforts to reduce that burden.